[Nouveau] [PATCH drm-misc-next v6 3/6] drm/gpuvm: add an abstraction for a VM / BO combination
Thomas Hellström
thomas.hellstrom at linux.intel.com
Tue Oct 17 10:54:47 UTC 2023
Hi,
On 10/17/23 11:58, Danilo Krummrich wrote:
> On Fri, Oct 13, 2023 at 02:30:29PM +0200, Thomas Hellström wrote:
>> On Mon, 2023-10-09 at 01:32 +0200, Danilo Krummrich wrote:
>>> Add an abstraction layer between the drm_gpuva mappings of a
>>> particular
>>> drm_gem_object and this GEM object itself. The abstraction represents
>>> a
>>> combination of a drm_gem_object and drm_gpuvm. The drm_gem_object
>>> holds
>>> a list of drm_gpuvm_bo structures (the structure representing this
>>> abstraction), while each drm_gpuvm_bo contains list of mappings of
>>> this
>>> GEM object.
>>>
>>> This has multiple advantages:
>>>
>>> 1) We can use the drm_gpuvm_bo structure to attach it to various
>>> lists
>>> of the drm_gpuvm. This is useful for tracking external and evicted
>>> objects per VM, which is introduced in subsequent patches.
>>>
>>> 2) Finding mappings of a certain drm_gem_object mapped in a certain
>>> drm_gpuvm becomes much cheaper.
>>>
>>> 3) Drivers can derive and extend the structure to easily represent
>>> driver specific states of a BO for a certain GPUVM.
>>>
>>> The idea of this abstraction was taken from amdgpu, hence the credit
>>> for
>>> this idea goes to the developers of amdgpu.
>>>
>>> Cc: Christian König <christian.koenig at amd.com>
>>> Signed-off-by: Danilo Krummrich <dakr at redhat.com>
>>> ---
>>> drivers/gpu/drm/drm_gpuvm.c | 332 +++++++++++++++++++++--
>>> --
>>> drivers/gpu/drm/nouveau/nouveau_uvmm.c | 64 +++--
>>> include/drm/drm_gem.h | 32 +--
>>> include/drm/drm_gpuvm.h | 177 ++++++++++++-
>>> 4 files changed, 521 insertions(+), 84 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/drm_gpuvm.c
>>> b/drivers/gpu/drm/drm_gpuvm.c
>>> index 6368dfdbe9dd..28282283ddaf 100644
>>> --- a/drivers/gpu/drm/drm_gpuvm.c
>>> +++ b/drivers/gpu/drm/drm_gpuvm.c
>>> @@ -70,6 +70,18 @@
>>> * &drm_gem_object, such as the &drm_gem_object containing the root
>>> page table,
>>> * but it can also be a 'dummy' object, which can be allocated with
>>> * drm_gpuvm_root_object_alloc().
>>> + *
>>> + * In order to connect a struct drm_gpuva its backing
>>> &drm_gem_object each
>> NIT: Same as previous patch regarding kerneldoc references
> I was intentionally using generic references here to make the documentation
> more readable while still keeping references to be able to look up the
> structure's fields.
>
>>> + * &drm_gem_object maintains a list of &drm_gpuvm_bo structures, and
>>> each
>>> + * &drm_gpuvm_bo contains a list of &&drm_gpuva structures.
>>> + *
>>> + * A &drm_gpuvm_bo is an abstraction that represents a combination
>>> of a
>>> + * &drm_gpuvm and a &drm_gem_object. Every such combination should
>>> be unique.
>>> + * This is ensured by the API through drm_gpuvm_bo_obtain() and
>>> + * drm_gpuvm_bo_obtain_prealloc() which first look into the
>>> corresponding
>>> + * &drm_gem_object list of &drm_gpuvm_bos for an existing instance
>>> of this
>>> + * particular combination. If not existent a new instance is created
>>> and linked
>>> + * to the &drm_gem_object.
>>> */
>>>
>>> /**
>>> @@ -395,21 +407,28 @@
>>> /**
>>> * DOC: Locking
>>> *
>>> - * Generally, the GPU VA manager does not take care of locking
>>> itself, it is
>>> - * the drivers responsibility to take care about locking. Drivers
>>> might want to
>>> - * protect the following operations: inserting, removing and
>>> iterating
>>> - * &drm_gpuva objects as well as generating all kinds of operations,
>>> such as
>>> - * split / merge or prefetch.
>>> - *
>>> - * The GPU VA manager also does not take care of the locking of the
>>> backing
>>> - * &drm_gem_object buffers GPU VA lists by itself; drivers are
>>> responsible to
>>> - * enforce mutual exclusion using either the GEMs dma_resv lock or
>>> alternatively
>>> - * a driver specific external lock. For the latter see also
>>> - * drm_gem_gpuva_set_lock().
>>> - *
>>> - * However, the GPU VA manager contains lockdep checks to ensure
>>> callers of its
>>> - * API hold the corresponding lock whenever the &drm_gem_objects GPU
>>> VA list is
>>> - * accessed by functions such as drm_gpuva_link() or
>>> drm_gpuva_unlink().
>>> + * In terms of managing &drm_gpuva entries DRM GPUVM does not take
>>> care of
>>> + * locking itself, it is the drivers responsibility to take care
>>> about locking.
>>> + * Drivers might want to protect the following operations:
>>> inserting, removing
>>> + * and iterating &drm_gpuva objects as well as generating all kinds
>>> of
>>> + * operations, such as split / merge or prefetch.
>>> + *
>>> + * DRM GPUVM also does not take care of the locking of the backing
>>> + * &drm_gem_object buffers GPU VA lists and &drm_gpuvm_bo
>>> abstractions by
>>> + * itself; drivers are responsible to enforce mutual exclusion using
>>> either the
>>> + * GEMs dma_resv lock or alternatively a driver specific external
>>> lock. For the
>>> + * latter see also drm_gem_gpuva_set_lock().
>>> + *
>>> + * However, DRM GPUVM contains lockdep checks to ensure callers of
>>> its API hold
>>> + * the corresponding lock whenever the &drm_gem_objects GPU VA list
>>> is accessed
>>> + * by functions such as drm_gpuva_link() or drm_gpuva_unlink(), but
>>> also
>>> + * drm_gpuvm_bo_obtain() and drm_gpuvm_bo_put().
>>> + *
>>> + * The latter is required since on creation and destruction of a
>>> &drm_gpuvm_bo
>>> + * the &drm_gpuvm_bo is attached / removed from the &drm_gem_objects
>>> gpuva list.
>>> + * Subsequent calls to drm_gpuvm_bo_obtain() for the same &drm_gpuvm
>>> and
>>> + * &drm_gem_object must be able to observe previous creations and
>>> destructions
>>> + * of &drm_gpuvm_bos in order to keep instances unique.
>>> */
>>>
>>> /**
>>> @@ -439,6 +458,7 @@
>>> * {
>>> * struct drm_gpuva_ops *ops;
>>> * struct drm_gpuva_op *op
>>> + * struct drm_gpuvm_bo *vm_bo;
>>> *
>>> * driver_lock_va_space();
>>> * ops = drm_gpuvm_sm_map_ops_create(gpuvm, addr, range,
>>> @@ -446,6 +466,10 @@
>>> * if (IS_ERR(ops))
>>> * return PTR_ERR(ops);
>>> *
>>> + * vm_bo = drm_gpuvm_bo_obtain(gpuvm, obj);
>>> + * if (IS_ERR(vm_bo))
>>> + * return PTR_ERR(vm_bo);
>>> + *
>>> * drm_gpuva_for_each_op(op, ops) {
>>> * struct drm_gpuva *va;
>>> *
>>> @@ -458,7 +482,7 @@
>>> *
>>> * driver_vm_map();
>>> * drm_gpuva_map(gpuvm, va, &op->map);
>>> - * drm_gpuva_link(va);
>>> + * drm_gpuva_link(va, vm_bo);
>>> *
>>> * break;
>>> * case DRM_GPUVA_OP_REMAP: {
>>> @@ -485,11 +509,11 @@
>>> * driver_vm_remap();
>>> * drm_gpuva_remap(prev, next, &op-
>>>> remap);
>>> *
>>> - * drm_gpuva_unlink(va);
>>> * if (prev)
>>> - * drm_gpuva_link(prev);
>>> + * drm_gpuva_link(prev, va-
>>>> vm_bo);
>>> * if (next)
>>> - * drm_gpuva_link(next);
>>> + * drm_gpuva_link(next, va-
>>>> vm_bo);
>>> + * drm_gpuva_unlink(va);
>>> *
>>> * break;
>>> * }
>>> @@ -505,6 +529,7 @@
>>> * break;
>>> * }
>>> * }
>>> + * drm_gpuvm_bo_put(vm_bo);
>>> * driver_unlock_va_space();
>>> *
>>> * return 0;
>>> @@ -514,6 +539,7 @@
>>> *
>>> * struct driver_context {
>>> * struct drm_gpuvm *gpuvm;
>>> + * struct drm_gpuvm_bo *vm_bo;
>>> * struct drm_gpuva *new_va;
>>> * struct drm_gpuva *prev_va;
>>> * struct drm_gpuva *next_va;
>>> @@ -534,6 +560,7 @@
>>> * struct drm_gem_object *obj, u64
>>> offset)
>>> * {
>>> * struct driver_context ctx;
>>> + * struct drm_gpuvm_bo *vm_bo;
>>> * struct drm_gpuva_ops *ops;
>>> * struct drm_gpuva_op *op;
>>> * int ret = 0;
>>> @@ -543,16 +570,23 @@
>>> * ctx.new_va = kzalloc(sizeof(*ctx.new_va),
>>> GFP_KERNEL);
>>> * ctx.prev_va = kzalloc(sizeof(*ctx.prev_va),
>>> GFP_KERNEL);
>>> * ctx.next_va = kzalloc(sizeof(*ctx.next_va),
>>> GFP_KERNEL);
>>> - * if (!ctx.new_va || !ctx.prev_va || !ctx.next_va) {
>>> + * ctx.vm_bo = drm_gpuvm_bo_create(gpuvm, obj);
>>> + * if (!ctx.new_va || !ctx.prev_va || !ctx.next_va ||
>>> !vm_bo) {
>>> * ret = -ENOMEM;
>>> * goto out;
>>> * }
>>> *
>>> + * // Typically protected with a driver specific GEM
>>> gpuva lock
>>> + * // used in the fence signaling path for
>>> drm_gpuva_link() and
>>> + * // drm_gpuva_unlink(), hence pre-allocate.
>>> + * ctx.vm_bo = drm_gpuvm_bo_obtain_prealloc(ctx.vm_bo);
>>> + *
>>> * driver_lock_va_space();
>>> * ret = drm_gpuvm_sm_map(gpuvm, &ctx, addr, range, obj,
>>> offset);
>>> * driver_unlock_va_space();
>>> *
>>> * out:
>>> + * drm_gpuvm_bo_put(ctx.vm_bo);
>>> * kfree(ctx.new_va);
>>> * kfree(ctx.prev_va);
>>> * kfree(ctx.next_va);
>>> @@ -565,7 +599,7 @@
>>> *
>>> * drm_gpuva_map(ctx->vm, ctx->new_va, &op->map);
>>> *
>>> - * drm_gpuva_link(ctx->new_va);
>>> + * drm_gpuva_link(ctx->new_va, ctx->vm_bo);
>>> *
>>> * // prevent the new GPUVA from being freed in
>>> * // driver_mapping_create()
>>> @@ -577,22 +611,23 @@
>>> * int driver_gpuva_remap(struct drm_gpuva_op *op, void *__ctx)
>>> * {
>>> * struct driver_context *ctx = __ctx;
>>> + * struct drm_gpuva *va = op->remap.unmap->va;
>>> *
>>> * drm_gpuva_remap(ctx->prev_va, ctx->next_va, &op-
>>>> remap);
>>> *
>>> - * drm_gpuva_unlink(op->remap.unmap->va);
>>> - * kfree(op->remap.unmap->va);
>>> - *
>>> * if (op->remap.prev) {
>>> - * drm_gpuva_link(ctx->prev_va);
>>> + * drm_gpuva_link(ctx->prev_va, va->vm_bo);
>>> * ctx->prev_va = NULL;
>>> * }
>>> *
>>> * if (op->remap.next) {
>>> - * drm_gpuva_link(ctx->next_va);
>>> + * drm_gpuva_link(ctx->next_va, va->vm_bo);
>>> * ctx->next_va = NULL;
>>> * }
>>> *
>>> + * drm_gpuva_unlink(va);
>>> + * kfree(va);
>>> + *
>>> * return 0;
>>> * }
>>> *
>>> @@ -771,6 +806,194 @@ drm_gpuvm_destroy(struct drm_gpuvm *gpuvm)
>>> }
>>> EXPORT_SYMBOL_GPL(drm_gpuvm_destroy);
>>>
>>> +/**
>>> + * drm_gpuvm_bo_create() - create a new instance of struct
>>> drm_gpuvm_bo
>>> + * @gpuvm: The &drm_gpuvm the @obj is mapped in.
>>> + * @obj: The &drm_gem_object being mapped in the @gpuvm.
>>> + *
>>> + * If provided by the driver, this function uses the &drm_gpuvm_ops
>>> + * vm_bo_alloc() callback to allocate.
>>> + *
>>> + * Returns: a pointer to the &drm_gpuvm_bo on success, NULL on
>> Kerneldoc uses "Return:" rather than "Returns:", (This seems to a
>> common thing throughout the series).
> Gonna fix.
>
>>> failure
>>> + */
>>> +struct drm_gpuvm_bo *
>> Any particular reason there's line-break after the function type even
>> when it fits the ~100 char limit?
> Nope, just for consistency thoughout this source file.
>
>>> +drm_gpuvm_bo_create(struct drm_gpuvm *gpuvm,
>>> + struct drm_gem_object *obj)
>>
>>
>>> +{
>>> + const struct drm_gpuvm_ops *ops = gpuvm->ops;
>>> + struct drm_gpuvm_bo *vm_bo;
>>> +
>>> + if (ops && ops->vm_bo_alloc)
>>> + vm_bo = ops->vm_bo_alloc();
>>> + else
>>> + vm_bo = kzalloc(sizeof(*vm_bo), GFP_KERNEL);
>>> +
>>> + if (unlikely(!vm_bo))
>>> + return NULL;
>>> +
>>> + vm_bo->vm = gpuvm;
>>> + vm_bo->obj = obj;
>>> +
>>> + kref_init(&vm_bo->kref);
>>> + INIT_LIST_HEAD(&vm_bo->list.gpuva);
>>> + INIT_LIST_HEAD(&vm_bo->list.entry.gem);
>>> +
>>> + drm_gem_object_get(obj);
>> Perhaps group this with the vm_bo->obj assignment to emphasize that
>> that's the pointer that gets the reference?
> Yep, makes sense.
>
>>> +
>>> + return vm_bo;
>>> +}
>>> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_create);
>>> +
>>> +static void
>>> +drm_gpuvm_bo_destroy(struct kref *kref)
>>> +{
>>> + struct drm_gpuvm_bo *vm_bo = container_of(kref, struct
>>> drm_gpuvm_bo,
>>> + kref);
>>> + struct drm_gpuvm *gpuvm = vm_bo->vm;
>>> + const struct drm_gpuvm_ops *ops = gpuvm->ops;
>>> + struct drm_gem_object *obj = vm_bo->obj;
>>> + bool lock = !drm_gpuvm_resv_protected(gpuvm);
>>> +
>>> + drm_gem_gpuva_assert_lock_held(obj);
>>> + if (!lock)
>>> + drm_gpuvm_resv_assert_held(gpuvm);
>>> +
>>> + list_del(&vm_bo->list.entry.gem);
>>> +
>>> + drm_gem_object_put(obj);
>> Not sure if we have any drivers utilizing vm_bo_free() yet, but it
>> might make sense to move the drm_gem_object_put() until after the
>> freeing below, in case vm_bo_free() wants to use it?
> Good point, gonna fix.
>
>>> +
>>> + if (ops && ops->vm_bo_free)
>>> + ops->vm_bo_free(vm_bo);
>>> + else
>>> + kfree(vm_bo);
>>> +}
>>> +
>>> +/**
>>> + * drm_gpuvm_bo_put() - drop a struct drm_gpuvm_bo reference
>>> + * @vm_bo: the &drm_gpuvm_bo to release the reference of
>>> + *
>>> + * This releases a reference to @vm_bo.
>>> + *
>>> + * If the reference count drops to zero, the &gpuvm_bo is destroyed,
>>> which
>>> + * includes removing it from the GEMs gpuva list. Hence, if a call
>>> to this
>>> + * function can potentially let the reference count to zero the
>>> caller must
>>> + * hold the dma-resv or driver specific GEM gpuva lock.
>>> + */
>>> +void
>>> +drm_gpuvm_bo_put(struct drm_gpuvm_bo *vm_bo)
>>> +{
>>> + if (vm_bo)
>>> + kref_put(&vm_bo->kref, drm_gpuvm_bo_destroy);
>>> +}
>>> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_put);
>>> +
>>> +static struct drm_gpuvm_bo *
>>> +__drm_gpuvm_bo_find(struct drm_gpuvm *gpuvm,
>>> + struct drm_gem_object *obj)
>>> +{
>>> + struct drm_gpuvm_bo *vm_bo;
>>> +
>>> + drm_gem_gpuva_assert_lock_held(obj);
>>> +
>>> + drm_gem_for_each_gpuvm_bo(vm_bo, obj)
>>> + if (vm_bo->vm == gpuvm)
>>> + return vm_bo;
>>> +
>>> + return NULL;
>>> +}
>>> +
>>> +/**
>>> + * drm_gpuvm_bo_find() - find the &drm_gpuvm_bo for the given
>>> + * &drm_gpuvm and &drm_gem_object
>>> + * @gpuvm: The &drm_gpuvm the @obj is mapped in.
>>> + * @obj: The &drm_gem_object being mapped in the @gpuvm.
>>> + *
>>> + * Find the &drm_gpuvm_bo representing the combination of the given
>>> + * &drm_gpuvm and &drm_gem_object. If found, increases the reference
>>> + * count of the &drm_gpuvm_bo accordingly.
>>> + *
>>> + * Returns: a pointer to the &drm_gpuvm_bo on success, NULL on
>>> failure
>>> + */
>>> +struct drm_gpuvm_bo *
>>> +drm_gpuvm_bo_find(struct drm_gpuvm *gpuvm,
>>> + struct drm_gem_object *obj)
>>> +{
>>> + struct drm_gpuvm_bo *vm_bo = __drm_gpuvm_bo_find(gpuvm, obj);
>>> +
>>> + return vm_bo ? drm_gpuvm_bo_get(vm_bo) : NULL;
>>> +}
>>> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_find);
>>> +
>>> +/**
>>> + * drm_gpuvm_bo_obtain() - obtains and instance of the &drm_gpuvm_bo
>>> for the
>>> + * given &drm_gpuvm and &drm_gem_object
>>> + * @gpuvm: The &drm_gpuvm the @obj is mapped in.
>>> + * @obj: The &drm_gem_object being mapped in the @gpuvm.
>>> + *
>>> + * Find the &drm_gpuvm_bo representing the combination of the given
>>> + * &drm_gpuvm and &drm_gem_object. If found, increases the reference
>>> + * count of the &drm_gpuvm_bo accordingly. If not found, allocates a
>>> new
>>> + * &drm_gpuvm_bo.
>>> + *
>>> + * A new &drm_gpuvm_bo is added to the GEMs gpuva list.
>>> + *
>>> + * Returns: a pointer to the &drm_gpuvm_bo on success, an ERR_PTR on
>>> failure
>>> + */
>>> +struct drm_gpuvm_bo *
>>> +drm_gpuvm_bo_obtain(struct drm_gpuvm *gpuvm,
>>> + struct drm_gem_object *obj)
>>> +{
>>> + struct drm_gpuvm_bo *vm_bo;
>>> +
>>> + vm_bo = drm_gpuvm_bo_find(gpuvm, obj);
>>> + if (vm_bo)
>>> + return vm_bo;
>>> +
>>> + vm_bo = drm_gpuvm_bo_create(gpuvm, obj);
>>> + if (!vm_bo)
>>> + return ERR_PTR(-ENOMEM);
>>> +
>>> + list_add_tail(&vm_bo->list.entry.gem, &obj->gpuva.list);
>> Lockdep check?
> Is inherited by drm_gpuvm_bo_find(), but I can also be explicit here.
>
>>> +
>>> + return vm_bo;
>>> +}
>>> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_obtain);
>>> +
>>> +/**
>>> + * drm_gpuvm_bo_obtain_prealloc() - obtains and instance of the
>>> &drm_gpuvm_bo
>>> + * for the given &drm_gpuvm and &drm_gem_object
>>> + * @__vm_bo: A pre-allocated struct drm_gpuvm_bo.
>>> + *
>>> + * Find the &drm_gpuvm_bo representing the combination of the given
>>> + * &drm_gpuvm and &drm_gem_object. If found, increases the reference
>>> + * count of the found &drm_gpuvm_bo accordingly, while the @__vm_bo
>>> reference
>>> + * count is decreased. If not found @__vm_bo is returned without
>>> further
>>> + * increase of the reference count.
>>> + *
>>> + * A new &drm_gpuvm_bo is added to the GEMs gpuva list.
>>> + *
>>> + * Returns: a pointer to the found &drm_gpuvm_bo or @__vm_bo if no
>>> existing
>>> + * &drm_gpuvm_bo was found
>>> + */
>>> +struct drm_gpuvm_bo *
>>> +drm_gpuvm_bo_obtain_prealloc(struct drm_gpuvm_bo *__vm_bo)
>>> +{
>>> + struct drm_gpuvm *gpuvm = __vm_bo->vm;
>>> + struct drm_gem_object *obj = __vm_bo->obj;
>>> + struct drm_gpuvm_bo *vm_bo;
>>> +
>>> + vm_bo = drm_gpuvm_bo_find(gpuvm, obj);
>>> + if (vm_bo) {
>>> + drm_gpuvm_bo_put(__vm_bo);
>>> + return vm_bo;
>>> + }
>>> +
>>> + list_add_tail(&__vm_bo->list.entry.gem, &obj->gpuva.list);
>> Perhaps a lockdep check here?
> Same as above.
>
>>> +
>>> + return __vm_bo;
>>> +}
>>> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_obtain_prealloc);
>>> +
>>> static int
>>> __drm_gpuva_insert(struct drm_gpuvm *gpuvm,
>>> struct drm_gpuva *va)
>>> @@ -860,24 +1083,33 @@ EXPORT_SYMBOL_GPL(drm_gpuva_remove);
>>> /**
>>> * drm_gpuva_link() - link a &drm_gpuva
>>> * @va: the &drm_gpuva to link
>>> + * @vm_bo: the &drm_gpuvm_bo to add the &drm_gpuva to
>>> *
>>> - * This adds the given &va to the GPU VA list of the &drm_gem_object
>>> it is
>>> - * associated with.
>>> + * This adds the given &va to the GPU VA list of the &drm_gpuvm_bo
>>> and the
>>> + * &drm_gpuvm_bo to the &drm_gem_object it is associated with.
>>> + *
>>> + * For every &drm_gpuva entry added to the &drm_gpuvm_bo an
>>> additional
>>> + * reference of the latter is taken.
>>> *
>>> * This function expects the caller to protect the GEM's GPUVA list
>>> against
>> NIT: Referring to a "gem object" as a "GEM" catches my eye every time.
>> Perhaps that has become common practice? With my "it used to be like.."
>> hat on, I'd use gem object.
> I think this is the way it referred to in a lot of places, e.g. drm_exe.c,
> drm_gem.c, etc. Hence, I'd like to stick with that.
>
>>> - * concurrent access using the GEMs dma_resv lock.
>>> + * concurrent access using either the GEMs dma_resv lock or a driver
>>> specific
>>> + * lock set through drm_gem_gpuva_set_lock().
>>> */
>>> void
>>> -drm_gpuva_link(struct drm_gpuva *va)
>>> +drm_gpuva_link(struct drm_gpuva *va, struct drm_gpuvm_bo *vm_bo)
>>> {
>>> struct drm_gem_object *obj = va->gem.obj;
>>>
>>> if (unlikely(!obj))
>>> return;
>>>
>>> + WARN_ON(obj != vm_bo->obj);
>> Can we use drm_WARN here?
> Sure!
>
>>> drm_gem_gpuva_assert_lock_held(obj);
>>>
>>> - list_add_tail(&va->gem.entry, &obj->gpuva.list);
>>> + drm_gpuvm_bo_get(vm_bo);
>>> +
>>> + va->vm_bo = vm_bo;
>>> + list_add_tail(&va->gem.entry, &vm_bo->list.gpuva);
>>> }
>>> EXPORT_SYMBOL_GPL(drm_gpuva_link);
>>>
>>> @@ -888,13 +1120,22 @@ EXPORT_SYMBOL_GPL(drm_gpuva_link);
>>> * This removes the given &va from the GPU VA list of the
>>> &drm_gem_object it is
>>> * associated with.
>>> *
>>> + * This removes the given &va from the GPU VA list of the
>>> &drm_gpuvm_bo and
>>> + * the &drm_gpuvm_bo from the &drm_gem_object it is associated with
>>> in case
>>> + * this call unlinks the last &drm_gpuva from the &drm_gpuvm_bo.
>>> + *
>>> + * For every &drm_gpuva entry removed from the &drm_gpuvm_bo a
>>> reference of
>>> + * the latter is dropped.
>>> + *
>>> * This function expects the caller to protect the GEM's GPUVA list
>>> against
>>> - * concurrent access using the GEMs dma_resv lock.
>>> + * concurrent access using either the GEMs dma_resv lock or a driver
>>> specific
>>> + * lock set through drm_gem_gpuva_set_lock().
>>> */
>>> void
>>> drm_gpuva_unlink(struct drm_gpuva *va)
>>> {
>>> struct drm_gem_object *obj = va->gem.obj;
>>> + struct drm_gpuvm_bo *vm_bo = va->vm_bo;
>>>
>>> if (unlikely(!obj))
>>> return;
>>> @@ -902,6 +1143,9 @@ drm_gpuva_unlink(struct drm_gpuva *va)
>>> drm_gem_gpuva_assert_lock_held(obj);
>>>
>>> list_del_init(&va->gem.entry);
>>> + va->vm_bo = NULL;
>>> +
>>> + drm_gpuvm_bo_put(vm_bo);
>>> }
>>> EXPORT_SYMBOL_GPL(drm_gpuva_unlink);
>>>
>>> @@ -1046,10 +1290,10 @@ drm_gpuva_remap(struct drm_gpuva *prev,
>>> struct drm_gpuva *next,
>>> struct drm_gpuva_op_remap *op)
>>> {
>>> - struct drm_gpuva *curr = op->unmap->va;
>>> - struct drm_gpuvm *gpuvm = curr->vm;
>>> + struct drm_gpuva *va = op->unmap->va;
>>> + struct drm_gpuvm *gpuvm = va->vm;
>>>
>>> - drm_gpuva_remove(curr);
>>> + drm_gpuva_remove(va);
>>>
>>> if (op->prev) {
>>> drm_gpuva_init_from_op(prev, op->prev);
>>> @@ -1693,9 +1937,8 @@ drm_gpuvm_prefetch_ops_create(struct drm_gpuvm
>>> *gpuvm,
>>> EXPORT_SYMBOL_GPL(drm_gpuvm_prefetch_ops_create);
>>>
>>> /**
>>> - * drm_gpuvm_gem_unmap_ops_create() - creates the &drm_gpuva_ops to
>>> unmap a GEM
>>> - * @gpuvm: the &drm_gpuvm representing the GPU VA space
>>> - * @obj: the &drm_gem_object to unmap
>>> + * drm_gpuvm_bo_unmap_ops_create() - creates the &drm_gpuva_ops to
>>> unmap a GEM
>>> + * @vm_bo: the &drm_gpuvm_bo abstraction
>>> *
>>> * This function creates a list of operations to perform unmapping
>>> for every
>>> * GPUVA attached to a GEM.
>>> @@ -1712,15 +1955,14 @@
>>> EXPORT_SYMBOL_GPL(drm_gpuvm_prefetch_ops_create);
>>> * Returns: a pointer to the &drm_gpuva_ops on success, an ERR_PTR
>>> on failure
>>> */
>>> struct drm_gpuva_ops *
>>> -drm_gpuvm_gem_unmap_ops_create(struct drm_gpuvm *gpuvm,
>>> - struct drm_gem_object *obj)
>>> +drm_gpuvm_bo_unmap_ops_create(struct drm_gpuvm_bo *vm_bo)
>>> {
>>> struct drm_gpuva_ops *ops;
>>> struct drm_gpuva_op *op;
>>> struct drm_gpuva *va;
>>> int ret;
>>>
>>> - drm_gem_gpuva_assert_lock_held(obj);
>>> + drm_gem_gpuva_assert_lock_held(vm_bo->obj);
>>>
>>> ops = kzalloc(sizeof(*ops), GFP_KERNEL);
>>> if (!ops)
>>> @@ -1728,8 +1970,8 @@ drm_gpuvm_gem_unmap_ops_create(struct drm_gpuvm
>>> *gpuvm,
>>>
>>> INIT_LIST_HEAD(&ops->list);
>>>
>>> - drm_gem_for_each_gpuva(va, obj) {
>>> - op = gpuva_op_alloc(gpuvm);
>>> + drm_gpuvm_bo_for_each_va(va, vm_bo) {
>>> + op = gpuva_op_alloc(vm_bo->vm);
>>> if (!op) {
>>> ret = -ENOMEM;
>>> goto err_free_ops;
>>> @@ -1743,10 +1985,10 @@ drm_gpuvm_gem_unmap_ops_create(struct
>>> drm_gpuvm *gpuvm,
>>> return ops;
>>>
>>> err_free_ops:
>>> - drm_gpuva_ops_free(gpuvm, ops);
>>> + drm_gpuva_ops_free(vm_bo->vm, ops);
>>> return ERR_PTR(ret);
>>> }
>>> -EXPORT_SYMBOL_GPL(drm_gpuvm_gem_unmap_ops_create);
>>> +EXPORT_SYMBOL_GPL(drm_gpuvm_bo_unmap_ops_create);
>>>
>>> /**
>>> * drm_gpuva_ops_free() - free the given &drm_gpuva_ops
>>> diff --git a/drivers/gpu/drm/nouveau/nouveau_uvmm.c
>>> b/drivers/gpu/drm/nouveau/nouveau_uvmm.c
>>> index 93ad2ba7ec8b..4e46f850e65f 100644
>>> --- a/drivers/gpu/drm/nouveau/nouveau_uvmm.c
>>> +++ b/drivers/gpu/drm/nouveau/nouveau_uvmm.c
>>> @@ -62,6 +62,8 @@ struct bind_job_op {
>>> enum vm_bind_op op;
>>> u32 flags;
>>>
>>> + struct drm_gpuvm_bo *vm_bo;
>>> +
>>> struct {
>>> u64 addr;
>>> u64 range;
>>> @@ -1113,22 +1115,28 @@ bind_validate_region(struct nouveau_job *job)
>>> }
>>>
>>> static void
>>> -bind_link_gpuvas(struct drm_gpuva_ops *ops, struct
>>> nouveau_uvma_prealloc *new)
>>> +bind_link_gpuvas(struct bind_job_op *bop)
>>> {
>>> + struct nouveau_uvma_prealloc *new = &bop->new;
>>> + struct drm_gpuvm_bo *vm_bo = bop->vm_bo;
>>> + struct drm_gpuva_ops *ops = bop->ops;
>>> struct drm_gpuva_op *op;
>>>
>>> drm_gpuva_for_each_op(op, ops) {
>>> switch (op->op) {
>>> case DRM_GPUVA_OP_MAP:
>>> - drm_gpuva_link(&new->map->va);
>>> + drm_gpuva_link(&new->map->va, vm_bo);
>>> break;
>>> - case DRM_GPUVA_OP_REMAP:
>>> + case DRM_GPUVA_OP_REMAP: {
>>> + struct drm_gpuva *va = op->remap.unmap->va;
>>> +
>>> if (op->remap.prev)
>>> - drm_gpuva_link(&new->prev->va);
>>> + drm_gpuva_link(&new->prev->va, va-
>>>> vm_bo);
>>> if (op->remap.next)
>>> - drm_gpuva_link(&new->next->va);
>>> - drm_gpuva_unlink(op->remap.unmap->va);
>>> + drm_gpuva_link(&new->next->va, va-
>>>> vm_bo);
>>> + drm_gpuva_unlink(va);
>>> break;
>>> + }
>>> case DRM_GPUVA_OP_UNMAP:
>>> drm_gpuva_unlink(op->unmap.va);
>>> break;
>>> @@ -1150,10 +1158,18 @@ nouveau_uvmm_bind_job_submit(struct
>>> nouveau_job *job)
>>>
>>> list_for_each_op(op, &bind_job->ops) {
>>> if (op->op == OP_MAP) {
>>> - op->gem.obj = drm_gem_object_lookup(job-
>>>> file_priv,
>>> - op-
>>>> gem.handle);
>>> - if (!op->gem.obj)
>>> + struct drm_gem_object *obj;
>>> +
>>> + obj = drm_gem_object_lookup(job->file_priv,
>>> + op->gem.handle);
>>> + if (!(op->gem.obj = obj))
>>> return -ENOENT;
>>> +
>>> + dma_resv_lock(obj->resv, NULL);
>>> + op->vm_bo = drm_gpuvm_bo_obtain(&uvmm->base,
>>> obj);
>>> + dma_resv_unlock(obj->resv);
>>> + if (IS_ERR(op->vm_bo))
>>> + return PTR_ERR(op->vm_bo);
>>> }
>>>
>>> ret = bind_validate_op(job, op);
>>> @@ -1364,7 +1380,7 @@ nouveau_uvmm_bind_job_submit(struct nouveau_job
>>> *job)
>>> case OP_UNMAP_SPARSE:
>>> case OP_MAP:
>>> case OP_UNMAP:
>>> - bind_link_gpuvas(op->ops, &op->new);
>>> + bind_link_gpuvas(op);
>>> break;
>>> default:
>>> break;
>>> @@ -1511,6 +1527,12 @@ nouveau_uvmm_bind_job_free_work_fn(struct
>>> work_struct *work)
>>> if (!IS_ERR_OR_NULL(op->ops))
>>> drm_gpuva_ops_free(&uvmm->base, op->ops);
>>>
>>> + if (!IS_ERR_OR_NULL(op->vm_bo)) {
>>> + dma_resv_lock(obj->resv, NULL);
>>> + drm_gpuvm_bo_put(op->vm_bo);
>>> + dma_resv_unlock(obj->resv);
>>> + }
>>> +
>>> if (obj)
>>> drm_gem_object_put(obj);
>>> }
>>> @@ -1776,15 +1798,18 @@ void
>>> nouveau_uvmm_bo_map_all(struct nouveau_bo *nvbo, struct nouveau_mem
>>> *mem)
>>> {
>>> struct drm_gem_object *obj = &nvbo->bo.base;
>>> + struct drm_gpuvm_bo *vm_bo;
>>> struct drm_gpuva *va;
>>>
>>> dma_resv_assert_held(obj->resv);
>>>
>>> - drm_gem_for_each_gpuva(va, obj) {
>>> - struct nouveau_uvma *uvma = uvma_from_va(va);
>>> + drm_gem_for_each_gpuvm_bo(vm_bo, obj) {
>>> + drm_gpuvm_bo_for_each_va(va, vm_bo) {
>>> + struct nouveau_uvma *uvma = uvma_from_va(va);
>>>
>>> - nouveau_uvma_map(uvma, mem);
>>> - drm_gpuva_invalidate(va, false);
>>> + nouveau_uvma_map(uvma, mem);
>>> + drm_gpuva_invalidate(va, false);
>>> + }
>>> }
>>> }
>>>
>>> @@ -1792,15 +1817,18 @@ void
>>> nouveau_uvmm_bo_unmap_all(struct nouveau_bo *nvbo)
>>> {
>>> struct drm_gem_object *obj = &nvbo->bo.base;
>>> + struct drm_gpuvm_bo *vm_bo;
>>> struct drm_gpuva *va;
>>>
>>> dma_resv_assert_held(obj->resv);
>>>
>>> - drm_gem_for_each_gpuva(va, obj) {
>>> - struct nouveau_uvma *uvma = uvma_from_va(va);
>>> + drm_gem_for_each_gpuvm_bo(vm_bo, obj) {
>>> + drm_gpuvm_bo_for_each_va(va, vm_bo) {
>>> + struct nouveau_uvma *uvma = uvma_from_va(va);
>>>
>>> - nouveau_uvma_unmap(uvma);
>>> - drm_gpuva_invalidate(va, true);
>>> + nouveau_uvma_unmap(uvma);
>>> + drm_gpuva_invalidate(va, true);
>>> + }
>>> }
>>> }
>>>
>>> diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
>>> index 16364487fde9..369505447acd 100644
>>> --- a/include/drm/drm_gem.h
>>> +++ b/include/drm/drm_gem.h
>>> @@ -580,7 +580,7 @@ int drm_gem_evict(struct drm_gem_object *obj);
>>> * drm_gem_gpuva_init() - initialize the gpuva list of a GEM object
>>> * @obj: the &drm_gem_object
>>> *
>>> - * This initializes the &drm_gem_object's &drm_gpuva list.
>>> + * This initializes the &drm_gem_object's &drm_gpuvm_bo list.
>>> *
>>> * Calling this function is only necessary for drivers intending to
>>> support the
>>> * &drm_driver_feature DRIVER_GEM_GPUVA.
>>> @@ -593,28 +593,28 @@ static inline void drm_gem_gpuva_init(struct
>>> drm_gem_object *obj)
>>> }
>>>
>>> /**
>>> - * drm_gem_for_each_gpuva() - iternator to walk over a list of
>>> gpuvas
>>> - * @entry__: &drm_gpuva structure to assign to in each iteration
>>> step
>>> - * @obj__: the &drm_gem_object the &drm_gpuvas to walk are
>>> associated with
>>> + * drm_gem_for_each_gpuvm_bo() - iterator to walk over a list of
>>> &drm_gpuvm_bo
>>> + * @entry__: &drm_gpuvm_bo structure to assign to in each iteration
>>> step
>>> + * @obj__: the &drm_gem_object the &drm_gpuvm_bo to walk are
>>> associated with
>>> *
>>> - * This iterator walks over all &drm_gpuva structures associated
>>> with the
>>> - * &drm_gpuva_manager.
>>> + * This iterator walks over all &drm_gpuvm_bo structures associated
>>> with the
>>> + * &drm_gem_object.
>>> */
>>> -#define drm_gem_for_each_gpuva(entry__, obj__) \
>>> - list_for_each_entry(entry__, &(obj__)->gpuva.list, gem.entry)
>>> +#define drm_gem_for_each_gpuvm_bo(entry__, obj__) \
>>> + list_for_each_entry(entry__, &(obj__)->gpuva.list,
>>> list.entry.gem)
>>>
>>> /**
>>> - * drm_gem_for_each_gpuva_safe() - iternator to safely walk over a
>>> list of
>>> - * gpuvas
>>> - * @entry__: &drm_gpuva structure to assign to in each iteration
>>> step
>>> - * @next__: &next &drm_gpuva to store the next step
>>> - * @obj__: the &drm_gem_object the &drm_gpuvas to walk are
>>> associated with
>>> + * drm_gem_for_each_gpuvm_bo_safe() - iterator to safely walk over a
>>> list of
>>> + * &drm_gpuvm_bo
>>> + * @entry__: &drm_gpuvm_bostructure to assign to in each iteration
>>> step
>>> + * @next__: &next &drm_gpuvm_bo to store the next step
>>> + * @obj__: the &drm_gem_object the &drm_gpuvm_bo to walk are
>>> associated with
>>> *
>>> - * This iterator walks over all &drm_gpuva structures associated
>>> with the
>>> + * This iterator walks over all &drm_gpuvm_bo structures associated
>>> with the
>>> * &drm_gem_object. It is implemented with
>>> list_for_each_entry_safe(), hence
>>> * it is save against removal of elements.
>>> */
>>> -#define drm_gem_for_each_gpuva_safe(entry__, next__, obj__) \
>>> - list_for_each_entry_safe(entry__, next__, &(obj__)-
>>>> gpuva.list, gem.entry)
>>> +#define drm_gem_for_each_gpuvm_bo_safe(entry__, next__, obj__) \
>>> + list_for_each_entry_safe(entry__, next__, &(obj__)-
>>>> gpuva.list, list.entry.gem)
>>>
>>> #endif /* __DRM_GEM_H__ */
>>> diff --git a/include/drm/drm_gpuvm.h b/include/drm/drm_gpuvm.h
>>> index 13539f32c2e2..ddb0b8d323cf 100644
>>> --- a/include/drm/drm_gpuvm.h
>>> +++ b/include/drm/drm_gpuvm.h
>>> @@ -26,12 +26,14 @@
>>> */
>>>
>>> #include <linux/list.h>
>>> +#include <linux/dma-resv.h>
>>> #include <linux/rbtree.h>
>>> #include <linux/types.h>
>>>
>>> #include <drm/drm_gem.h>
>>>
>>> struct drm_gpuvm;
>>> +struct drm_gpuvm_bo;
>>> struct drm_gpuvm_ops;
>>>
>>> /**
>>> @@ -72,6 +74,12 @@ struct drm_gpuva {
>>> */
>>> struct drm_gpuvm *vm;
>>>
>>> + /**
>>> + * @vm_bo: the &drm_gpuvm_bo abstraction for the mapped
>>> + * &drm_gem_object
>>> + */
>>> + struct drm_gpuvm_bo *vm_bo;
>>> +
>>> /**
>>> * @flags: the &drm_gpuva_flags for this mapping
>>> */
>>> @@ -107,7 +115,7 @@ struct drm_gpuva {
>>> struct drm_gem_object *obj;
>>>
>>> /**
>>> - * @entry: the &list_head to attach this object to a
>>> &drm_gem_object
>>> + * @entry: the &list_head to attach this object to a
>>> &drm_gpuvm_bo
>>> */
>>> struct list_head entry;
>>> } gem;
>>> @@ -140,7 +148,7 @@ struct drm_gpuva {
>>> int drm_gpuva_insert(struct drm_gpuvm *gpuvm, struct drm_gpuva *va);
>>> void drm_gpuva_remove(struct drm_gpuva *va);
>>>
>>> -void drm_gpuva_link(struct drm_gpuva *va);
>>> +void drm_gpuva_link(struct drm_gpuva *va, struct drm_gpuvm_bo
>>> *vm_bo);
>>> void drm_gpuva_unlink(struct drm_gpuva *va);
>>>
>>> struct drm_gpuva *drm_gpuva_find(struct drm_gpuvm *gpuvm,
>>> @@ -187,10 +195,16 @@ static inline bool drm_gpuva_invalidated(struct
>>> drm_gpuva *va)
>>> * enum drm_gpuvm_flags - flags for struct drm_gpuvm
>>> */
>>> enum drm_gpuvm_flags {
>>> + /**
>>> + * @DRM_GPUVM_RESV_PROTECTED: GPUVM is protected externally
>>> by the
>>> + * GPUVM's &dma_resv lock
>>> + */
>>> + DRM_GPUVM_RESV_PROTECTED = (1 << 0),
>>> +
>>> /**
>>> * @DRM_GPUVM_USERBITS: user defined bits
>>> */
>>> - DRM_GPUVM_USERBITS = (1 << 0),
>>> + DRM_GPUVM_USERBITS = (1 << 1),
>>> };
>>>
>>> /**
>>> @@ -272,6 +286,19 @@ bool drm_gpuvm_interval_empty(struct drm_gpuvm
>>> *gpuvm, u64 addr, u64 range);
>>> struct drm_gem_object *
>>> drm_gpuvm_root_object_alloc(struct drm_device *drm);
>>>
>>> +/**
>>> + * drm_gpuvm_resv_protected() - indicates whether
>>> &DRM_GPUVM_RESV_PROTECTED is
>>> + * set
>>> + * @gpuvm: the &drm_gpuvm
>>> + *
>>> + * Returns: true if &DRM_GPUVM_RESV_PROTECTED is set, false
>>> otherwise.
>>> + */
>>> +static inline bool
>>> +drm_gpuvm_resv_protected(struct drm_gpuvm *gpuvm)
>>> +{
>>> + return gpuvm->flags & DRM_GPUVM_RESV_PROTECTED;
>>> +}
>>> +
>>> /**
>>> * drm_gpuvm_resv() - returns the &drm_gpuvm's &dma_resv
>>> * @gpuvm__: the &drm_gpuvm
>>> @@ -290,6 +317,12 @@ drm_gpuvm_root_object_alloc(struct drm_device
>>> *drm);
>>> */
>>> #define drm_gpuvm_resv_obj(gpuvm__) ((gpuvm__)->r_obj)
>>>
>>> +#define drm_gpuvm_resv_held(gpuvm__) \
>>> + dma_resv_held(drm_gpuvm_resv(gpuvm__))
>>> +
>>> +#define drm_gpuvm_resv_assert_held(gpuvm__) \
>>> + dma_resv_assert_held(drm_gpuvm_resv(gpuvm__))
>>> +
>>> #define drm_gpuvm_resv_held(gpuvm__) \
>>> dma_resv_held(drm_gpuvm_resv(gpuvm__))
>>>
>>> @@ -374,6 +407,117 @@ __drm_gpuva_next(struct drm_gpuva *va)
>>> #define drm_gpuvm_for_each_va_safe(va__, next__, gpuvm__) \
>>> list_for_each_entry_safe(va__, next__, &(gpuvm__)->rb.list,
>>> rb.entry)
>>>
>>> +/**
>>> + * struct drm_gpuvm_bo - structure representing a &drm_gpuvm and
>>> + * &drm_gem_object combination
>>> + *
>>> + * This structure is an abstraction representing a &drm_gpuvm and
>>> + * &drm_gem_object combination. It serves as an indirection to
>>> accelerate
>>> + * iterating all &drm_gpuvas within a &drm_gpuvm backed by the same
>>> + * &drm_gem_object.
>>> + *
>>> + * Furthermore it is used cache evicted GEM objects for a certain
>>> GPU-VM to
>>> + * accelerate validation.
>>> + *
>>> + * Typically, drivers want to create an instance of a struct
>>> drm_gpuvm_bo once
>>> + * a GEM object is mapped first in a GPU-VM and release the instance
>>> once the
>>> + * last mapping of the GEM object in this GPU-VM is unmapped.
>>> + */
>>> +struct drm_gpuvm_bo {
>>> +
>>> + /**
>>> + * @vm: The &drm_gpuvm the @obj is mapped in.
>> Not refcounted. @vm may potentially be freed under us in the
>> !RESV_PROTECTED case.
> It's the drivers responsibility to ensure the VM is not freed up as long as
> VM_BOs with this VM do exist. However, this is nothing drivers need to care
> about explicitly, since drivers are responsible to keep the VM alive as long
> as mappings exist anyway. And all mappings being gone implies also all VM_BOs
> being gone, since the lifetime of a VM_BO goes from the first mapping backed by
> a certain object is created to the last mapping backed by this object is
> removed. drm_gpuvm_destroy() will also warn if the GPUVM still contains
> mappings.
>
> I will document this more explicitly somewhere.
>
>>> + */
>>> + struct drm_gpuvm *vm;
>>> +
>>> + /**
>>> + * @obj: The &drm_gem_object being mapped in @vm.
>> Refcounted pointer.
> Guess you want me to document that.
Yes, that'd be good. Especially with internal lower-level locking it
will become crucial to know where we have strong vs weak referencing so
we know where to upgrade with kref_get_unless_zero().
Thanks,
Thomas
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